MEASUREMENT AND ANALYSIS OF VEHICLE COMFORT AND ROAD QUALITY

The suspension system of a vehicle is an essential component because it is related to the dynamic performance of the vehicle. It ensures the tire-grounding contact, absorbing the oscillations excited by the road, and maintains the stability of the vehicle by distributing the wheel forces, providing comfort and safety to vehicle occupants. Structurally it links the vehicle sprung mass to the unsprung mass, and it connects to other subsystems, such as the steering and the brake components. In order to analysis and design a suspension system, several models that simulate the suspension dynamics behavior are available, however each has a different level of complexity and the accuracy of the results varies. Thus, the aim of this study was to compare a quarter car model with the real dynamics of a vehicle using a Matlab simulation. A test vehicle was instrumented with three-axis accelerometers, through which data on the acceleration of the sprung mass and unsprung mass was obtained when the vehicle was excited by a speed bump. From this simulation, it was possible to perform a model update to obtain the approximate vehicle parameters. The road surface quality plays a fundamental role in the vehicle oscillation and therefore in the comfort of the vehicle occupants. Using the instrumented vehicle and the adjusted parameters of the model, some routes along different pavement types in the city of Joinville were chosen to collect the vibration data in a vehicular test. The results were used to determine the international roughness index (IRI), an index to evaluate road quality. It was verified that the city roads with high IRI values, for instance, on streets paved with cobble stones, are associated with greater discomfort to passengers inside the vehicle, reflecting a low quality of the pavement. In contrast, lower IRI values are obtained for roads with a higher quality surface, resulting in greater comfort for the passengers.